Folate binding proteins in liver and kidney are being purified and characterized by an in vivo technique. Administered labeled folate is reduced and converted to polyglutamate derivatives. Four separate binding proteins have been identified in liver which bind primarily polyglutamate forms of folate. Another binding protein has been found in the plasma membrane portion which binds unchanged folic acid. In the kidney only a single binding protein has been identified. Further work is being carried out on the purification and characterization of these problems. BIBLIOGRAPHIC REFERENCES: Chen, Chi-Po, and Wagner, C. "Folate Transport in the Chorid Plexus". Life Sciences. 16, 1571-1582, (1975). Zamierowski, M., and Wagner, C. "The Characterization of High Molecular Weight Complexes of Folic Acid in Mammalian Tissues". Vth International Pteridine Symposium, proceedings. April, 1975.